title: Thanatophoric dysplasia type I: new radiologic, morphologic, and histologic aspects toward the exact definition of the disorder.
abstract: A comprehensive seven-step study on THANATOPHORIC DYSPLASIA without cloverleaf skull (TD Type I) was carried out postmortem on three aborted fetuses of 19, 26-27, and 34 weeks and one preterm neonate of 35 weeks gestation, respectively. The characteristic x-ray configuration of the spine in TD Type I presenting with H-, U- or reversed U-shape vertebrae were shown to correlate with the inclination or reclination of the vertebral bodies within a kyphotic or lordotic segment. The bowing of the tubular bones in TD Type I is explained by a diminished mechanical stability that is causally related to a specific cartilage structure. The perichondral spurs are defined by their morphologic structure, and their origin is attributed to a normal perichondral ossification in the presence of an impaired enchondral ossification. Impairment of enchondral ossification was more evident in the periphery than in the center of the metaphyses leading to a tongue-shaped osseous cone directed toward the epiphysis. The perichondral spurs and the linguiform enchondral growth plate resulted in a three-phase maple leaf-like contour of the metaphyses of tubular bones and acetabular roof. The nature of the perichondral fibrous bands, the fibrovascular bundles, and the fibrovascular bands of the growth plate and their significance in atypical ossification processes are discussed in detail. It is suggested that the diminished longitudinal growth of the skeleton is caused by a reduced mitotic activity of cartilage cells in the proliferative zone leading to a reduction of cell numbers in the columnar zone transversely oriented spongiosa bars resulting from desmal ossification of the metaphyseal fibrovascular structures.
authors.affiliation: Orthopaedic University Hospital, Rheinische Westfäliche Technische Hochschule Aachen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Weber
authors.forename: T
authors.initials: T
authors.lastname: Johannissón
authors.forename: M
authors.initials: M
authors.lastname: Thomsen
authors.forename: H
authors.initials: H
authors.lastname: Rehder
authors.forename: F U
authors.initials: FU
authors.lastname: Niethard
mesh_terms: D001842:Bone and Bones / Q000000981:diagnostic imaging; D002356:Cartilage / Q000473:pathology; D005260:Female; D006132:Growth Plate / Q000473:pathology; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009999:Ossification, Heterotopic; D010012:Osteogenesis; D011859:Radiography; D013131:Spine / Q000000981:diagnostic imaging / Q000473:pathology; D013796:Thanatophoric Dysplasia / Q000145:classification* / Q000000981:diagnostic imaging / Q000196:embryology / Q000473:pathology